Methyl tert-butyl ether (MTBE) was the most common fuel oxygenate throughout the 1990s and has become a widespread and persistent pollutant of water resources. Although the use of MTBE has now been banned in several states, it will continue to be a problematic groundwater contaminant for decades to come. There is an increasing interest in the development of effective technologies to remediate MTBE-contaminated sites, for instance pump-and-treat techniques, biostimulation, and bioaugmentation. The full-scale implementation of these techniques is considerably costly and is currently economically applicable for a few sites with highly sensitive receptors. Therefore, the fate of MTBE in the environment is mainly dependent upon natural remediation processes. Anaerobic biodegradation is a potential means for remediation of contaminated aquifers and has been observed under different redox conditions, but no responsible organisms have yet been identified. For anaerobic biodegradation to be a reliable method of natural attenuation or enhanced biodegradation of contaminated aquifers, we need further information about the organisms mediating the process.
Our research aims at developing tools for monitored natural attenuation of methyl tert-butyl ether. We have demonstrated that anaerobic MTBE degradation can occur under different anoxic conditions, and may be an important process in anoxic environments. Anaerobic degradation of MTBE results in significant carbon isotope fractionation, demonstrating that compound specific isotope analysis can be used as an indicator for in situ degradation. In our current work we are identifying the organisms that mediate anaerobic MTBE-degradation in anaerobic laboratory cultures in order to develop molecular tools for monitoring natural or enhanced attenuation of MTBE. We are also developing the use of plant-phenolic co-substrates to enhance anaerobic MTBE degradation. Many aryl O-methyl ethers, such as syringic acid, that are O-demethylated by acetogenic bacteria, were also O-demethylated by the MTBE-utilizing enrichment cultures. The addition of these compounds as co-substrates increased the rate of MTBE-degradation
The aim of our current work is to identify the organisms that mediate anaerobic MTBE-degradation in anaerobic laboratory cultures in order to develop molecular tools for monitoring natural or enhanced attenuation of MTBE. Anaerobic enrichment cultures maintained with MTBE as the sole carbon source for over a decade are subjected to molecular community analyses in order to identify the bacterial species that are enriched during the degradation process. Identification of the microorganisms mediating anaerobic MTBE degradation will provide the foundation for developing tools for site assessment and bioremediation monitoring.
The goal is to extend the laboratory work to monitor natural attenuation and enhanced biodegradation of MTBE at select field sites. Specifically, we are 1) using complementary molecular tools to identify microorganisms present in anaerobic MTBE-degrading laboratory cultures and at contaminated sites; 2) developing the use of stable isotope probing (SIP), with 13C-labeled MTBE to identify microorganisms responsible for anaerobic MTBE-degradation; and 3) assessing the potential for stimulating anaerobic MTBE degradation at different sites though the addition of appropriate co-substrates and amendments.
Researchers: Laura Youngster
Publications:
Youngster LKG, Somsamak P, Häggblom MM (2008) Effects of co-substrates and inhibitors on the anaerobic O-demethylation of methyl tert-butyl ether (MTBE). Appl. Microbiol. Biotechnol. 80:1113-1120.
Häggblom MM, Youngster LKG, Somsamak P, Richnow HH (2007) Anaerobic biodegradation of methyl tert-butyl ether (MTBE) and related fuel oxygenates. Advances in Applied Microbiology 62:1-20.
Rosell M, Häggblom MM, Richnow H-H (2007) Compound specific isotope analysis (CSIA) to characterise degradation pathways and to quantify in situ degradation of fuel oxygenates and other fuel derived contaminants. In: The Handbook of Environmental Chemistry (ed. O. Hutzinger & D. Barcelo) Vol. 5 Part R, pp. 99-119.
Somsamak P, Richnow HH, Häggblom MM (2006) Carbon isotope fractionation during anaerobic degradation of methyl tert-butyl ether (MTBE) under sulfate-reducing and methanogenic conditions. Appl. Environ. Microbiol. 72:1157-1163.
Somsamak P, Richnow HH, Häggblom MM (2005) Carbon isotopic fractionation during anaerobic biotransformation of methyl tert-butyl ether and tert-amyl methyl ether. Environ. Sci. Technol. 39:103-109.
Somsamak P, Cowan RM, Häggblom MM (2001) Anaerobic biotransformation of fuel oxygenates under different anoxic conditions. FEMS Microbiol. Ecol. 37:259-264.
Funding:
New Jersey Department of Environmental Protection
New Jersey Water Resources Research Institute
Collaborators:
Lee Kerkhof, Rutgers, Institute of Marine and Coastal Sciences
http://marine.rutgers.edu/main/IMCS-People-Details/People-Details-Lee-J.-Kerkhof.html
Hans H. Richnow, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany.
http://www.ufz.de/index.php?en=5265
